The tobacco industry spends the largest share of its marketing budget at the point of sale, where it enjoys relatively few regulations. Stores saturated with tobacco advertising, promotions, and products constitute a significant public health concern, especially for youth. Research has shown that tobacco ads are more numerous in stores near schools, and in neighborhoods with a higher proportion of residents under age 18. Although several studies describe the quantity and nature of tobacco advertisements in stores, little is known about the impact of cumulative exposure to these messages on young people. A longitudinal study is proposed to measure adolescents' exposure to retail tobacco advertising and its influence on smoking initiation. The combination of data from student surveys and store observations is a unique feature of this research. The study will: (1) survey sixth, seventh, and eighth graders in a California community to assess their shopping habits, receptivity to tobacco marketing, and smoking-related beliefs and behaviors; (2) measure the density of tobacco advertising in a sample of retail tobacco outlets in the two communities; and (3) conduct follow-up surveys of the same students and observations of the same stores one year later. Adolescents' exposure to retail tobacco advertising will be measured by multiplying their self-reported frequency of visiting stores that sell tobacco and the density of advertising in those locations. The study will test whether baseline advertising exposure predicts progression toward smoking at follow-up, controlling for smoking by family and friends and other influences. Additional hypotheses concern the relationship between adolescents' exposure to tobacco advertising in stores and indicators of marketing receptivity, such as naming a favorite cigarette brand and owning or wanting a promotional item with a tobacco company name or logo. The study will also test whether the density of tobacco advertising is greater in stores where youth frequently shop. Few longitudinal studies examine the effects of tobacco advertising and promotions on youth, and none address in-store advertising. The proposed study addresses concerns that the proliferation of tobacco advertising in stores contributes to an environment that encourages youth to smoke. It also meets a pressing need for research about the possible causal role of retail tobacco advertising in the initiation of smoking.